Cyprinodontiformes

Cyprinodontiformes Temporal range: Oligocene–recent PreꞒ Ꞓ O S D C P T J K Pg N
Mummichog (Fundulus heteroclitus heteroclitus) Female (top right) and two males
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
(unranked):	Ovalentaria
Order:	Cyprinodontiformes L. S. Berg, 1940
Type species
Cyprinodon variegatus Lacépède, 1803
Suborders
Aplocheiloidei Cyprinodontoidei
Synonyms
Microcyprini Regan, 1909

Cyprinodontiformes /ˌsɪprɪnoʊˈdɒntɪfɔːrmiːz/ is an order of ray-finned fish, comprising mostly small, freshwater fish.^[1] Many popular aquarium fish, such as killifish and live-bearers, are included. They are closely related to the Atheriniformes and are occasionally included with them. A colloquial term for the order as a whole is toothcarps, though they are not actually close relatives of the true carps – the latter belong to the superorder Ostariophysi, while the toothcarps are Acanthopterygii.

The families of Cyprinodontiformes can be informally divided into three groups based on reproductive strategy: viviparous and ovoviviparous (all species give live birth), and oviparous (all species are egg-laying). The live-bearing groups differ in whether the young are carried to term within (ovoviviparous) or without (viviparous) an enclosing eggshell. Phylogenetically however, one of the two suborders – the Aplocheiloidei – contains oviparous species exclusively, as do two of the four superfamilies of the other suborder (the Cyprinodontoidea and Valencioidea of the Cyprinodontoidei). Vivipary and ovovivipary have evolved independently from oviparous ancestors, the latter possibly twice.